Ethyl Bromide → 2-Bromo-4'-ethylpropiophenone

Participants

Reaction Steps

Diethylcadmium is then prepared, as described in Example 8, from 63 g of ethyl bromide, 13.8 g of magnesium and 53 g of cadmium chloride. It is suspended in 400 ml of benzene, and a solution of 48.7 g of the previously prepared 4-ethylbenzoyl chloride diluted in 100 ml of benzene is then added dropwise, while cooling to below 10° C. After the addition, the mixture is stirred for one hour at ambient temperature and then for 2 hours at the reflux temperature. It is then cooled to 10° C. and poured onto a mixture of ice and salt, with stirring; the resulting mixture is filtered and the organic phase is separated from the filtrate, extracted twice with dilute sodium hydroxide solution, washed with water, dried over magnesium sulphate and evaporated. 48.4 g of an oily residue remain, which is distilled under a high vacuum (13 Pa). A fraction consisting of 35.6 g of virtually pure 4'-ethylpropiophenone passes over at between 65° and 80° C. In order to effect bromination of the propiophenone, 34.8 g thereof are dissolved in 1,000 ml of tetrahydrofuran, and 17.5 ml of pyrrolidinone and then 114 g of pyrrolidinone hydrotribromide are added. The mixture is heated under reflux, with stirring; it decolourises gradually and pyrrolidinone hydrobromide precipitates. The reaction is complete after one hour, the hydrobromide is filtered off and rinsed with ethyl acetate and the solvents are evaporated off from the filtrate. The partially crystalline, oily orange residue is taken up in a mixture of water and methylene chloride. The organic phase is separated off, washed twice with water, dried and evaporated in vacuo. The greenish oily residue is dissolved in toluene, pentane is added, a small greenish gummy fraction is filtered off on paper and the filtrate is evaporated. An oily residue remains, which is used as such in a subsequent step.

Provenance & Evidence